As used in the descriptions that follow, the term “meta-materials” refers to materials that possess unique macroscopic properties due to finer scale repetition or alterations of one or more secondary materials within the host material to alter the bulk body's dielectric or conductive properties.
“Electromagnetic Band-Gap” (EBG) materials, also known to those skilled in the art as “Photonic Band-Gap” materials, are meta-materials that contain one or more secondary phase dielectric inclusions that are organized in periodic array(s) with periodic spacing(s) having dimensions that are an appreciable amount of a center frequency's wavelength so as to cause constructive and destructive interference over a particular range of electromagnetic frequencies. An EBG material effectively attenuates frequencies that fall within in its bandgap or stopband as the periodic dielectric inclusions inhibit propagation due to the destructive interference of reflections off the periodic array.
The term “Perfect Electrical Conductor” (PEC) refers to an infinite conductive surface that causes electric field components of an electromagnetic wave incident upon the PEC to be totally reflected 180° out of phase with the incident wave.
The term “Perfect Magnetic Conductor” (PMC) refers to an imaginary surface generated by a periodic array of coupled inductor and capacitor elements that causes the electric field components of an electromagnetic wave incident upon the PMC to be totally reflected completely in phase with the incident wave. A finite dimension imperfect PMC can be practically constructed using meta-material construction techniques using dielectric material inclusions into a dielectric host that has suitable permittivity and permeability values and periodicity to simulate the coupled inductor and capacitor elements of the imaginary PMC. A PMC may alternatively be known as an artificial magnetic conductor (AMC).
The term “EGB Defect Resonator” refers to a resonant structure formed by selectively removing or eliminating one or more dielectric inclusion element(s) from the periodic array that forms the EGB meta-material in a manner that permits waves within a narrow frequency band of the EGB's bandgap or stopband to propagate freely through the medium and/or to be localized within a specific region of the meta-material dielectric defined by the defect.
RF electronic modules typically comprise one (or more) semiconductor chip(s) that is (are) connected to passive circuit elements (resistors, inductors, and capacitors) and/or other discrete circuit elements such as diodes, transistor switches, SAW filters, baluns, or impedance matching networks, among others, through a passive interconnect structure. The passive interconnect structure is formed by routing electrical signals over conductor leads that are attached to the surface of an organic or ceramic dielectric layer or are embedded within said organic or ceramic dielectric layer. RF electronic modules represent the next generation of microelectronic integration in that they integrate the semiconductor die with additional components that cannot be manufactured integrally to the semiconductor IC as a single part. Modules are gaining popularity in large market applications because they reduce part count and conversion costs to the OEM. In cost sensitive product applications, modules having an interconnect structure that is formed with organic dielectric are preferred; however, in applications that utilize signals operating at high frequency (e.g., f≧1 GHz) or that are subject to high thermal loads, more expensive ceramic dielectrics may be used to reduce absorptive dielectric loss and boost signal integrity. Therefore, a module containing a passive ceramic interconnect structure that offers low-cost and improved signal integrity has great value in wireless circuit applications.
Wireless circuits are used to form a network connection between a mobile platform (such as a cell phone or laptop computer) and are finding increasing application in fixed local area networks as well as radar systems, due to their low cost and easy installation. Radio communications are managed through the device's RF front-end, which will typically operate near to or at GHz signaling frequencies where the insertion loss of passive circuit components is widely known to increase.
The power budget is often a prime concern in mobile platform design, so methods that minimize insertion loss among components used to assemble the front-end have great value. For instance, the front-end of a CDMA cell phone may typically contain a power amplifier (PA) die, a duplexer switch that alternately modulates transmit and receive modes to the antenna, an isolator circuit, and a switch/diplexer component that discriminates individual frequencies of interest. This front-end circuitry will typically impose roughly 4 dB of signal loss, so most high power PA die are designed to accommodate 4 dB of loss between PA's output port and the antenna's feed point. Therefore, methods that can reduce this loss would extend battery life by allowing the power budget dedicated to radio broadcast to operate significantly longer than a conventional front-end circuit.
Signal loss is minimized in the module by limiting the overall length the signal must travel between the PA and the antenna, decreasing the signal loss per unit length along the transmission line(s) used to direct the signal from the PA to the antenna, minimizing the number of loss generating components that are needed to process the signal(s) along that path, and by ensuring excellent impedance match along the entire path between the signal source (the PA) and the antenna so as to minimize reflected energy along that path.
Physical size is another critical issue in mobile platform design. Today's state of the art has reduced the size of a cell phone's front end to an area that is roughly 1.5 inch2. Therefore, an invention that would allow the entire function of an RF front end to be reduced in size to an area that is roughly the size of a PA die (4 mm×4 mm or 0.02 inch) has great value.
Physical size requirements are greater in interconnect structures that permit semiconductor dies to be flip-chip mounted on the interconnect structure. Input/output (I/O) contact pads 101 such as shown in FIG. 1 are mounted on the surface of the dielectric 111 in which conventional interconnect structures 103 are embedded, causing wells 105 to be formed between the pads 101 protruding from the dielectric's surface. Solder masks 107 are used to prevent solder balls 109 that connect the interconnect structure 103 to the semiconductor die 113 from wicking into the wells 105 during reflow processing and forming short circuits between adjacent pads. Recent increases in semiconductor integration have produced I/O pad pitches that are beyond solder mask manufacturing tolerances. This forces many module manufacturers to backside mount the semiconductor die and connect it to the interconnect structure through wire bonds located on the die's periphery, which then occupies a larger footprint. Therefore, modules that have I/O pads embedded within the dielectric of the interconnect structure, thereby allowing high-density semiconductor die to be flip-chip mounted within a wireless circuit are significant and have great value.
U.S. Pat. No. 6,027,826 to de Rochemont, et al., disclose articles and methods to form oxide ceramic on metal substrates to form laminate, filament and wire metal-ceramic composite structures using liquid aerosol spray techniques. U.S. Pat. Nos. 6,323,549 and 6,742,249 to de Rochemont, et al., disclose articles that comprise, and methods to construct, an interconnect structure that electrically contacts a semiconductor chip to a larger system using at least on discrete wire that is embedded in silica ceramic, as well as methods to embed passive components within said interconnect structure. U.S. Pat. Nos. 5,707,715 and 6,143,432 to de Rochemont, et al., disclose articles and methods to relieve thermally-induced mechanical stress in metal-ceramic circuit boards and metal-ceramic and ceramic-ceramic composite structures. The contents of each of these references are incorporated herein by reference as if laid out in their entirety.